The next point is defense.
Ok, so here is a common scenario. You have two countries back to back, with an enemy country bordering one. What tends to happen, is that you will build up a lav wall, with mortars and so on defening on either side.
What is often a favourable option, is to fall back from that bordering country to the border of the rear country. this is often most profitable when the rear county is a medium or large resource producer.
This is favourible for two reasons. the first is that it thrusts your opponent into a mobile role when he may well have set up with static attack in mind. if he has a wall of lavs then thats a lot of apcs needed. if he throws them in one by one you will chew them up. also, if he invests in tanks, they have the 5 hit points for 2$ as opposed to 8 hit points, making them easier to wear down.
On a phsycological note, if the front country of yours has indemnity, then your opponents eyes will light up and he will throw all his units into the grinder, hopefully leaving you to concentrate on perfecting your static defence while keeping the option to steam forward at any time. While falling back appears to hand the initiative to the enemy, in fact it does quite the opposite if handled correctly.
Important note; if he brings enough firepower to bear to clear all your units (lavs) from the front country in one turn, then you have lost the gamble and are in a very poor position. plan for this and maintain a large enough beach head in the front country.
Usefull units for support here are the rocket launcher and planes in support, as they can take out APC's in one turn. APC's have 3 hitpoints for 2$, and you are forcing your opponents hand into using them. Take them out as a general top priority in this situation. He will either keep his apc's back and so reducing thier usefullness while keeping thier cost; or spend more money on replacing them than he would like.
In a situation such as this where there is a coastal landing zone, take every opportunity to attack a naval transport with one bomber from a city of three bombers, as next turn that juicy transport can be picked off with all your bombers.
Above all, dont use this when your fighting me, or ill get annoyed and have to think of something even more crafty